It is a constant struggle in the art to find methods for improving the melt strength of a polymer melt composition so that it can be subjected to more stresses during processing. Low melt strength polymers can not be easily shaped or formed and thus are difficult and expensive to process. In contrast, high melt strength polymers process easier and do not require special handling.
Sorbitol and other such nucleating agents are known for their use in polyolefins, especially polypropylene, to alter the crystallization rate of the polyolefin. Specifically, sorbitol is used in polypropylene to increase the crystallization rate thus decreasing time spent in a mold waiting for the resin to harden. Sorbitol and like nucleating agents are also used in ascorbic acid fermentation, in cosmetic creams and lotions, toothpastes, tobaccos, gelatins, bodying agents (for paper, textiles, and liquid pharmaceuticals), softeners (candy), sugar crystallization inhibitors, surfactants (urethane resins and rigid foams), plasticisers, stabilizers for vinyl resins, food additives, sweeteners, humectants, emulsifiers, thickeners, anti-caking agents and dietary supplements. These agents, however, have not been used before to modify the rheology of a polyolefin.